1. Field of the Invention
The invention relates to a heater and a heating device with heaters. The invention relates especially to a heater and a heating device with heaters for irradiating an article to be processed with light which is emitted for purposes of heating of the object to be processed.
2. Description of Related Art
In general, thermal processing is used in the production of semiconductors in different processes, such as layer formation, oxidation diffusion, diffusion of impurities, nitriding, layer stabilization, silicide generation, crystallization, ion implantation-activation and the like. To improve the yield and the quality in the production of semiconductors, rapid thermal processing (RTP) is desired, in which the temperature of an article to be processed, such as a semiconductor wafer or the like, is rapidly raised or lowered. In RTP, a thermal processing device of the light irradiation type using light irradiation from a light source, such as a filament lamp or the like, is popularly used.
In a filament lamp in which there is a filament within a bulb of transparent material, at least 90% of the input power is completely radiated, and heating of the article to be heated without contact is possible. Therefore, the filament lamp is a lamp in which light can be used as heat. In the case of using such a filament lamp as a heat source for heating a glass substrate or a semiconductor wafer, the temperature of the article to be heated can be raised or lowered more quickly than in a resistance heating process.
This means that thermal processing of the light irradiation type can, for example, raise the temperature of the article to be processed to at least 1000° C. within ten to a few dozen seconds. The article to be processed is rapidly cooled after light irradiation is stopped. This thermal processing of the light irradiation type is normally carried out several times.
When the article to be processed is, for example, a semiconductor wafer, and if no uniformity of the temperature distribution is caused in the semiconductor wafer during heating, there is the possibility that a defect of crystal transition occurs, that is, a phenomenon called slip in the semiconductor wafer, and inferior goods will be formed. Therefore, in the case of carrying out RTP of a semiconductor wafer using a thermal processing device of the light irradiation type, it is necessary to carry out heating to obtain a high temperature, maintaining the high temperature and cooling such that the temperature distribution on the entire surface of the semiconductor wafer is made uniform. That is, in RTP, highly precise uniformity of the temperature of the article to be processed is required.
Japanese patent publication JP-A-HEI 7-37833 discloses, as a conventional heating device, one in which light which is emitted from a filament lamp is used to heat a glass substrate or a semiconductor wafer. As is shown in FIG. 11, this heating device is arranged such that an article to be processed is mounted within a chamber which has been formed from a transparent material, on the top and the bottom, therefore on both sides, outside this chamber there are several filament lamps arranged opposite each other at the top and bottom, and moreover, crossing one another, and that these filament lamps irradiate the article to be processed from the two sides with light and thus heat it.
FIG. 12 is a perspective in which the above described device is shown simplified and the heating filament lamps which are located on the top and bottom, i.e., on the two sides, and the article to be processed are not shown. As is shown in the drawing, the heating filament lamps which are located on the top and bottom, i.e., on the two sides, are arranged such that the tube axes cross. Therefore, the article to be processed can be uniformly heated. Moreover, with this device a temperature decrease because of the heat radiation action in the edge area of the article to be processed can be further prevented. By the measure that, with respect to the article to be processed, the lamp output of the heating filament lamps L1, L2 on the two ends of the top side is made larger than the lamp output of the heating lamps L3 in the middle area, the temperature of the edge areas A1-A2, B1-B2 of the area to be processed can be increased. Furthermore, the temperature of the edge areas A1-B1, A2-B2 of the area to be processed can be increased by the measure that, with respect to the article to be processed, the lamp output of the heating filament lamps L4, L5 on the two ends of the bottom side is made larger than the lamp output of a heating lamps L6 in the middle area.
However, it was found that the disadvantage described below arises in the above described conventional heating device. Specifically, when the article to be processed is, for example, a semiconductor wafer, a metal oxide film is formed on the surface of the semiconductor wafer by a sputtering process or the like, and impurities are doped in the semiconductor wafer by ion implantation. There are cases in which a temperature distribution occurs in the semiconductor wafer by the influence of the following factors that are deviations in the film thickness of such a metal oxide and deviations in the implantation conditions of the impurity ions. Such a temperature distribution is not limited to the linear edge areas A1-A2, B1-B2, A1-B1, A2-B2 and the like as shown in FIG. 12, but can occur in a narrow area such as, for example, only in the peripheral region of the A1 area.
Using the above described conventional heating device, the temperature drop in the linear areas, like in the edge areas A1-A2, B1-B2, A1-B1, A2-B2 or the like of the article to be processed can be prevented. However, in the case in which, in the linear edge area A1-A2 as shown in FIG. 12, the vicinity of the A1 area and the vicinity of the B1 area exhibit different temperature reduction tendencies, the two cannot be adjusted to one suitable temperature. This means that the temperature cannot be controlled in a narrow area, resulting in the following disadvantages:                a temperature distribution occurs in the processing temperature of the article to be processed and        the functions which are desired for t he article to be processed are adversely affected by it.        
Here, for example, in Japanese patent application publication JP-A-2002-203804 and corresponding U.S. patent application publication US 2004/0112885 A1, a thermal processing device is disclosed as is shown in FIG. 13. This device in a lamp housing comprises a first lamp unit for which there are several U-shaped, double-ended lamps arranged in the parallel and perpendicular directions with respect to the page of the drawings, in which there are feed devices for the filaments on the two ends of a bulb; and a second lamp unit which is located underneath this first lamp unit and in which several straight, double-ended lamps are arranged along the page of the drawings in a direction which is perpendicular to the page of the drawings, in which feed devices for the filaments are located on the two ends of a bulb. This thermal processing device is used for thermal processing of an article to be processed, such as a semiconductor wafer or the like, which is located underneath the second lamp unit.
It is disclosed that, in such a thermal processing device, in the article to be processed, there is a device for adjusting the U-shaped lamps of the first lamp unit which are located above a terminal part to a high output in order to increase the temperature of the terminal part on a support ring which has the tendency to a temperature which is lower than the other areas and on which the article to be processed is placed.
Japanese patent application publication JP-A-2002-203804 and corresponding U.S. patent application publication US 2004/0112885 A1 show that such a thermal processing device is used essentially as follows:
First, the heating area of the semiconductor wafer, which is the article to be processed, is divided into several concentric, center-symmetrical zones. By a combination of the distributions of the illuminance of the lamps of the first and second lamp units, patterns of the combined distributions of the illuminance are formed which correspond to the respective zone and which are center-symmetrical to the middle of the semiconductor wafer. Thus, heating is carried out according to the temperature change of the respective zone. Here, to suppress the effect of variations of the illuminance of the light from the lamps, the semiconductor wafer, which is the article to be processed, is turned. This means that heating of the respective zone which is arranged concentrically with an individual illuminance is possible.
Therefore, the technology described in Japanese patent application publication JP-A-2002-203804 and corresponding U.S. patent application publication US 2004/0112885 A1 enables the temperature to be controlled in a narrow region of the article to be processed. It can be imagined that the above described disadvantage can thus be advantageously eliminated; but, the following disadvantages occur in such a thermal processing device in practice.
The U-shaped lamps each consist of a horizontal part and a pair of vertical parts. However, only the horizontal part in which the filament is located contributes to emission. Between the filament located within the respective lamp and the filament located within the lamp which is adjacent to the horizontal part of the lamp on the same axis, there are two silica glass walls which form the respective vertical part. Furthermore, on the boundary between the horizontal part and the vertical part, a curved surface is formed, by which the horizontal part and the vertical part are formed integrally with one another. Therefore, between the adjacent filaments there is a space with a rather large overall length which does not contribute to emission. As a result, it can be imagined that the disadvantage arises that a nonuniformity of temperature occurs in the area directly underneath this space.
This means that the illuminance changes (decreases) relatively drastically in the area directly underneath the above described space even by a combination of the distributions of the illuminance of the lamps of the first and second lamp units which correspond to the respective zone, and even by the combined distribution of the illuminance on the semiconductor wafer which is center-symmetrical. Therefore, it can be imagined that it is relatively difficult to reduce the temperature nonuniformity in the vicinity of the area directly underneath the above described space even if heating which corresponds to the temperature change of the respective zone is to be carried out.
Also, since, in such a thermal processing device, there has recently been the tendency to make the space (mainly in the vertical direction) for the arrangement of the lamp units extremely small, when using U-shaped lamps, a space is required which corresponds to the vertical part of the lamp. This thermal processing device is therefore not advantageous with respect to the saving of space in the vertical direction.